Derivative Financial Instruments Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Notional amount of foreign currency derivatives	$ 136,725	$ 129,037
Swedish kronor
Notional amount of foreign currency derivatives	106,658	98,385
British pound sterling
Notional amount of foreign currency derivatives	7,612	15,619
Australian dollar
Notional amount of foreign currency derivatives	4,247	7,022
Japanese yen
Notional amount of foreign currency derivatives	3,729	5,157
Euro
Notional amount of foreign currency derivatives	9,611	2,232
Brazilian real
Notional amount of foreign currency derivatives	3,897	0
Other
Notional amount of foreign currency derivatives	$ 971	$ 622